If you go to Reddit, you will still see their ads, be they obvious or hidden through disguising as user interaction (bots are more or less obvious, AI is at the stage where they can fake users). You drive engagement and site traffic. The only way to do anything disadvantegous to Reddit is to stop going to Reddit (if you also delete all your content they have less things to put inbetween ads for the remaining users). You are the product they offer to advertisers, be it through being the buyer for advertised things or providing content to put between the ads so the users who may buy those things don't only see ads. Your enjoyment of the platform is largely if not completely irrelevant from the corporate standpoint. If anything, your disgruntlement can make you engage more providing them with more content to put between ads.
There is no other way to protest for big subreddits currently. If you completely private your sub, reddit admins will replace you with mods that will keep it online.
The only real way to do it is to keep moderating, but make the content of the sub extremely boring, like just pictures of vacuums
What if we go after the advertisers? Hit spez right in the wallet.
I think that's somewhat what this trolling is doing. Advertisers don't want their ads to be next to a ton of "fuck Spez" or unmoderated comments. Similarly, they target ads at specific subs and changing what the sub is about subverts that targeting.